Improvement in steam-generators



UNITED `STATES f PATENT QFFIGE.

THOMAS MITCHELL, OF ALBANY, `NEW YORIL Specification forming part of Letters `Patent No. 56,778, dated July 31, 1866.

To all whom it may concern:

Be it known that I, THOMAS MITCHELL, of Albany,in `the county of Albany and State of New York, `have invented a new and Improved Machine for Generating Steam,which is to take the place of steam-boilers, and I do hereby declare that the following is a full, clear, and

exact description of the same, reference being had to the annexed drawings, making a part of this specification.

Figure l is an outside view of the steamchamber. Fig. 2 is the water-tank.- Fig. 3 is the pressure-valve.

Similar letters of referenceindicate corresponding parts in the several figures.

This invention consists in the use of a steamtank, a pressure-valve, a water-tank, a forcepump, connecting-pipes, valves, cocks, expansion-rods, and damper-doors so made and connected that water is let into the steam-chamber when heated to the degree required, so that any given number of pounds of steam may be made instantaneous, and the quantity of water let in and graduated by the pressure of steam in the chamber.

This invention secures three important advantages in regard to steam-power: iirst, perfect safety against boiler-explosions; second, a saving of at least one-half the amount of fuel; and, thirdly, about three-fourths of the bulk, weight, and cost of steam-boilers, substantially as hereinafter described.

Letter A of Fig. l is a liuc, on the top of which the smoke-stack is placed, answering the purpose of a brace for the head and crownsheet of the chamber, increasing the steamsurface and a draft from the furnace. Letter B isa Water-distributer, made guttering and with an inclination downward from the flue, receiving the water from the pipe G, conducting a part of it to the walls of the chamber, and letting a part fall from the short gutters midway on the crown-sheet below. LettersD D are damper-doors, which serve the purpose of covering the draft-openings when down and shutting oft' the draft from the center ue when up, and also the al1-important one of covering and protecting the crown-sheet from being heated too hot. These doors are moved by the expansion-rod G, one end of which is fastened rmly in one side of the chamber and the other loose, so that when the degree of heat under the crown-sheet is obtained sufficiently high so as `to evaporate the water let into the chamber immediately, and yet not so high as to injure the crown-sheet at exactly this point, this rodhas expanded to such a length that it raises thedampers, covering the crown-sheet, and also covering completely the flue, shutting oif the draft from the chimney, and opening the doorsin the sides of chamber, giving a clear space for the cold air to pass through.

E is the lever, and which may be doubled to give a quicker motion,and by which the damperdoors are moved by the expansion-rods.

Fig. 2 is the water-tank, letter A of which is the pipe leading from a force-pump, through which the water is forced into the tank, keeping up a pressure in it enough to feed the chamber against any given pressure of steam. Letter B is the cock on the connecting-pipe between the water-tank and the steam-chamber, on which is a gear-wheel, and moved by the gear-rack connected with the lever C. This lever may also be doubled to give a quick motion to the cock.

Fig. 3 is the pressure-valve. Letters A A represent the pipe leading from the steamchamber into it, and thus always keeping the vpressure in the valve and the chamber equal.

There is rubber packing fastened between two flanges, (represented by the one under the dome on this valve,) the full size of the ange, separating the steam below the ange from the clear space above it under the dome.

B is the stem rising up through the center of the valve, on the lower end of which is a flat washer resting on the top lof the packing. C is a lever resting on the top of this stem or fulcrum. On the upper end of this lever is the gear-rack already described. It is clear from this that, the pressure being equal in the chamber and in this valve, thestem will rise and fall by the steam rising or falling, which it will do by exhausting any amount of steam from the chamber, and this fall will let the lever C fall also, which turns the cock on the connecting-pipe between the steam-chamber and the water-tank, and therefore turning the cock, and thus letting just water enough into the chamber, which is instantaneously evaporated into steam, to make up the quantity of steam thus exhausted, and which again instantly raises the stem on the pressure-valve, and thus again shutting oft' the Water from the tank and keeping it shut off until more steam is used by the running of the engine, or otherwise, and this action is continued as long as the ire is kept up in the furnace and the force-pump kept in motion. L

Letter D of Fig. 2 is a water-valve for the purpose of letting the -water off when the pressure is greater than required to feed the steam-chamber, and which is again conducted back into the reservoir by the pipe, if required for further use.

LetterF is the beam containing figures and niches, on any one of which the pea may be placed giving the pressure required to feed the chamber against any given number of pounds of steam. Ifsixty pounds are wanted, then set the pea on sixty-five pounds on the water-valve and sixty on the beam connected with lche pressure-valve. ln the same manner they are to be set to give any number of pounds of steam required. Y

The mode of operation is as follows: First, ire is made in the lire-box When there is no Water in the steam until the heat reaches a degree under the crown-sheet which lifts the damper-doors, at which point water is forced by hand with the force-pump, (detaching it from the engine for this purpose.) This is continued until the amount of steam required is obtained. When this is done the pump is again attached to the engine, and the steam being let on to it, as in ordinary cases, continues the action as long as is required.

It will'be seen by this invention that it is impossible for either water to accumulate in the chamber or the crown-sheet be injured by any amount of fire it is possible to make in the furnace.

It will also be seen that by putting rebricks in the nre-box the re cannot come in contact with the shell of the steam-chamber, which is, indeed, nothing but a single ordinary plate of boiler-iron.

It will also be seen that this machine is a most perfect Water and steam gage.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is-

The varrangement of the stem B or beam C G of Fig. 3 and cock B of Fig. 2, substantially as and for the purpose set forth.

THOS. MITCHELL.

Witnesses:

W. S. KELLEY, FRANCIS H. Woons. 

